Immunovant has unveiled the design of its phase 3 PROPEL trial, testing the drug imeroprubart in adults with generalized myasthenia gravis (gMG). The trial was presented at the 2026 AANEM Annual Meeting in Orlando, Florida, by researchers including Dr. Richard Nowak, director of the Yale Myasthenia Gravis Clinic.
Imeroprubart is an investigational neonatal Fc receptor (FcRn) blocker designed to reduce circulating immunoglobulin G (IgG), targeting the pathogenic IgG autoantibodies responsible for gMG. This mechanism represents a novel approach to treating the condition, particularly for patients who have not responded to conventional therapies.
Addressing Unmet Needs in gMG Treatment
According to investigators, 10% to 20% of gMG patients either do not achieve adequate disease control or experience intolerable side effects with current treatments. FcRn blockade offers a promising alternative by specifically targeting the underlying autoimmune mechanisms of gMG.
Imeroprubart differentiates itself from Immunovant’s earlier drug, batoclimab, by binding to FcRn in a way that minimizes the reduction in serum albumin, a side effect that led to cholesterol elevations with batoclimab. This distinction is critical, as it addresses a key safety concern observed in earlier FcRn blockers.
Trial Design and Objectives
PROPEL (NCT07039916) is a multicenter, randomized, placebo-controlled, double-blind trial led by Dr. Richard Nowak and colleagues. It aims to enroll approximately 231 adults aged 18 to 80 with mild to severe gMG, classified as Myasthenia Gravis Foundation of America Class II, III, or IVa. Participants must have an MG-ADL score of 6 or higher at screening and baseline. The trial includes both antibody-positive and seronegative patients.
Participants will receive 12 weekly subcutaneous doses of either imeroprubart 600 mg, imeroprubart 300 mg, or placebo, administered via autoinjector. This will be followed by 66 weeks of blinded active treatment. The primary endpoint is the change in MG-ADL score from baseline to week 12 in antibody-positive participants.
Key secondary endpoints include the change in Quantitative Myasthenia Gravis score, the proportion of patients achieving an MG-ADL score of 0 or 1, and the proportion with an MG-ADL improvement of 50% or more at week 12. These measures will provide a full assessment of imeroprubart’s efficacy in improving gMG symptoms.
Broader Implications and Future Prospects
PROPEL began enrolling in May 2025 and is ongoing at over 120 sites, with an estimated primary completion date of December 2028. Immunovant expects topline data from the gMG program in 2027, which could be key for the drug’s regulatory approval.
Immunovant has also reported interim data for imeroprubart in other autoimmune conditions. In rheumatoid arthritis, the drug demonstrated promising response rates, with 72.7% of patients achieving ACR20 at week 16. However, a proof-of-concept study in cutaneous lupus erythematosus did not meet its primary endpoint, leading to the discontinuation of that program. Despite this setback, Immunovant affirmed that development timelines for other indications, including gMG, remain on track.
Imeroprubart is further being investigated in chronic inflammatory demyelinating polyneuropathy, where enrollment continues in the phase 2b AMPLIFI trial, as well as in Graves’ disease and Sjogren’s disease. These studies show Immunovant’s commitment to exploring the drug’s potential across multiple autoimmune disorders.
